Former U.S. Treasury Secretary Timothy Geithner says he regrets not pushing for stronger financial safeguards ahead of the devastating 2008 crisis, according to reported excerpts of his new book.

“Before the crisis, I didn’t push for the Fed in Washington to strengthen the safeguards for banks, nor did I push for legislation in Congress to extend the safeguards to nonbanks,” he writes in Stress Test: Reflections on Financial Crises.

Excerpts published online in the New York Times Magazine reveal his behind-the-scenes view of the Wall Street meltdown that rocked the global economy. The book will be published Sunday.

Geithner, 52, said that he disagreed with Larry Summers, President Barack Obama’s chief economic adviser, and other members of the administration who were pushing Obama for the nationalization of some embattled banks like Citigroup.